How to stop my new boots from chafing and digging in to my heel?

I bought some bearpaw boots (ugg style) and I wore them for the first time today. The heel is really stiff and after a minute or two of walking they began to dig into the upper part of my heels by my ankle like near my achilles, and when I took them off the skin on both heels were red and raw. The boots fit my foot fine its just that the heel is really stiff, what can i do. I wasnt wearing socks because someone told me youre not supposed to wear them with these kinds of boots.